Laura competes in a triathlon in which she has to first swim, then bike, and then run for the same distance. She swims at a rate of 4 kilometres per hour, bikes at a rate of 20 kilometres per hour, and runs at a rate of 10 kilometres per hour. What is her average speed over the entire race?
The graph below shows the temperature (in degrees Celsius) over 10 weeks in Vancouver. Calculate the maximum range of variation (the difference between highest and lowest temperature).
In a 3-digit number, the hundreds digit is twice the tens digit while the units digit is thrice the tens digit. Also, the sum of its digits is 12. Find the number.